Cooler Fan Hub

ABSTRACT

The invention relates to an impeller wheel ( 1 ) as part of a fan for cooling a motor vehicle drive, in particular an internal combustion engine. The impeller wheel ( 1 ) can be set in rotation by a fan drive ( 10 ) having a drive shaft ( 8 ). The impeller wheel ( 1 ) has a cup-shaped basic form, including a base ( 3 ) for fastening the impeller wheel ( 1 ) on the drive shaft ( 8 ), a tubular section ( 4 ) which adjoins the base ( 3 ), and at least two impeller wheel blades ( 2 ) which are connected to the tubular section ( 4 ) and extend outward.

FIELD OF THE INVENTION

The invention relates to an impeller wheel as a constituent part of a fan for cooling a motor vehicle drive, in particular an internal combustion engine. The impeller wheel can be set in rotation by a fan drive which has a drive shaft, and which impeller wheel is cup shaped. The impeller includes: a base for fastening the impeller wheel on the drive shaft, a tubular section which adjoins the base, and at least two fan blades which are connected to the tubular section and extend outward.

BACKGROUND AND SUMMARY OF THE INVENTION

Energy liberated during the combustion in an internal combustion engine as a result of the exothermic, chemical conversion of the fuel is partially dissipated to the cylinder head and the cylinder block via the walls which delimit the combustion chamber and partially dissipated to the adjacent components and the surroundings via the exhaust gas flow. To keep the thermal loading of the components within limits, measures are undertaken to cool the cylinder block. The energy dissipated to the surroundings by the surface of the internal combustion engine via radiation and thermal conduction is insufficient for efficient cooling, thus cooling of the internal combustion engine is enhanced by forced convection.

Engine cooling can be by air cooling or liquid cooling, although liquid cooling is more common. In air cooling, the internal combustion engine is provided with a fan blower, the dissipation of energy by an air flow guided over the surface of the engine.

Internal combustion engines with liquid cooling have a coolant jacket, i.e., coolant channels arranged in the cylinder head which guides coolant through the cylinder head. Energy is transferred from the interior of the cylinder head to the coolant, typically water with additives. Coolant is circulated by a pump arranged in the cooling circuit. Energy transferred into the coolant from the head is then transferred in a heat exchanger. This heat exchanger is typically air cooled by a fan.

The fan ensures, among other things, that a sufficiently high air mass flow is provided when the vehicle is stationary. Typically, the fan drive is electrically operated.

The impeller wheel of a fan of the present invention is intended for use in both air and liquid cooling.

It is a problem in the design of fans and impeller wheels that both the drive shaft and the driven impeller wheel are dynamic, oscillatory systems. The impeller wheel is set in oscillation by the drive shaft. The drive shaft oscillates in a rotary manner by the temporally changing drive moments. Moreover, a deflection of the drive shaft along the longitudinal shaft axis causes a wobbling movement of the impeller wheel.

Vibrations degrade the component strength and cause component wear. Oscillations are also considered disadvantageous because of the audible noise which is disagreeable to the vehicle's occupants and others in the vicinity of the vehicle.

Increasing noise emission is an environmental problem affecting not only quality of life, but also the health of people exposed to it. A number of regulations have been established for limiting noise in Europe. The purchase decision of a potential customer is influenced by the noise of the vehicle. Thus, if noise can be reduced, both customers are better satisfied and noise regulations can be met.

Although the engine is the dominant noise source, all noise sources which contribute to the overall noise emission are considered.

SUMMARY OF THE INVENTION

Optimized acoustic behavior of a cooling fan is obtained by an impeller wheel which can be set in rotation by a fan drive which has a drive shaft. The impeller wheel has a cup-shaped basic form and has: a base for fastening the impeller wheel on the drive shaft, a tubular section which adjoins the base, and at least two fan blades which are connected to said tubular section and extend outward. The impeller wheel is distinguished by at least one aperture is provided in the base, which aperture makes pressure equalization possible between the outer side of the base and the inner side of the base.

Tests have shown that the base of a conventional impeller wheel is excited to oscillate. In the process acts like the cone of a loudspeaker, which leads to considerable noise emission.

In the impeller wheel according to an aspect of the present invention, an acoustic short-circuit is achieved by at least one aperture in the base of the impeller wheel. In a base which is excited to oscillate, at least one aperture ensures pressure equalization between the outer side of the base and the inner side of the base which faces the fan drive. This results in a reduced excitation of the adjacent air molecules and, as a consequence, in a reduction in the solid-borne sound radiation.

FIG. 1 shows by way of example, the measured sound pressure level, db(A), versus the rotational speed, N, of the fan drive or the drive shaft. The noise emission in Pascals [Pa] of a conventional impeller wheel (curve A) is contrasted with that of an embodiment of an impeller wheel according to an aspect of the invention (curve B). The impeller wheel according to an embodiment of the present invention has a plurality of apertures in the base, which ensures pressure equalization between the outer side and the inner side of the base.

The impeller wheel configured according to an embodiment of the invention leads to a reduction in the resonance which occurs in the conventional impeller wheel (curve A) at a shaft rotational speed of about N=1600 revolutions per minute.

In one embodiment, a plurality of apertures are distributed uniformly in the base region of the fan. The base of the fan is connected, typically screwed, to the center of the drive shaft. In one embodiment, the apertures are arranged spaced from the connecting location.

The aperture(s) can have any shape, as the reduction in noise does not depend on the specific design of the aperture, but depends on there being an opening, through which the air can flow from the outer side of the base to the inner side of the base and vice versa.

In one embodiment, at least one reinforcing rib is provided on the base; the at least one reinforcing rib is preferably to be arranged on the inner side of the base. The reinforcing rib increases the strength of the impeller wheel in the base region, with only a small amount of material. The additional material for forming the reinforcing rib adds an acceptably small weight increase in the impeller wheel.

An impeller wheel is disclosed in which at least one reinforcing rib is provided on the base. The rib strengthens the impeller wheel in the base region with only a small amount of material, which increases weight marginally. Also disclosed is at least one aperture space apart from the reinforcing rib.

In one embodiment, ribs are provided on the base extending substantially from the center of the base outward to the edge of the base. Alternatively, reinforcing ribs extend substantially radially. It is advantageous if the apertures are arranged between the ribs and have an orientation similar to the ribs.

In another embodiment, a cover is provided which is spaced apart from the outer side of the base. This cover protects the fan drive from corrosion and mechanical damage, such as the impact of stones. The fan drive is arranged on the inner side of the fan base which faces away from the outer side. The fan may be electrically operated.

The cover is spaced apart from the outer side of the base so that apertures which in the base are not closed by the cover. Otherwise, the desired pressure equalization would be prevented or suppressed between the outer and inner sides of the base.

In yet another embodiment, a damping material is provided between the outer side of the base and the cover. As a result, the air flow produced when the base oscillates and ensures pressure equalization between the outer side and the inner side of the base can be decelerated and therefore damped. However, the damping material ensures that, even though sufficient air for the pressure equalization passes through the apertures, no water spray passes through the apertures. Water spray could damage, for example, an electric drive which is arranged on the inner side of the base.

In another embodiment, a tubular section has at least one reinforcement element. The tubular section is preferably of rotationally symmetrical configuration, in particular cylindrical configuration, with respect to the longitudinal axis of the impeller wheel and imparts a cup-shaped basic shape to the impeller wheel or the center part of the impeller wheel together with the base. Here, the tubular section serves to accommodate the at least two fan blades which extend outward and is open on that side which faces away from the base, which permits the impeller wheel to be pushed onto the drive shaft in the context of the assembly of the fan. Here, the fan drive comes to rest in the final assembly position at least partially in the tubular section, with the result that the tubular section also serves as housing for the drive.

Tests have shown that the tubular section is deformed during fan operation. The rotating tubular section experiences a change in shape in its cross section. From a cylinder to an oval shape or a shape similar to an ellipse. The change in cross section is particularly pronounced at the open end of the tubular section and decreases in the direction of the impeller wheel base. This change in shape causes an adjustment of the at least two fan blades, the fan blades being inclined forward or rearward with respect to the longitudinal axis of the impeller wheel or with respect to the drive shaft. To counteract the above-described changes in shape, at least one reinforcement element of the tubular section may be provided. In one embodiment, the reinforcement element comprises a ring, the shape of which corresponds to the original cross section of the tubular section. The ring strengthens or supports the section. As the change in shape is particularly pronounced at the open side of the tubular section, in one embodiment, the reinforcement element is arranged as near as possible to the open side, that is to say the open end of the tubular section.

As the impeller wheel is a moving component, the reinforcement element may be manufactured substantially from a lightweight material.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph of sound pressure level vs. rotational speed of the fan drive for a conventional impeller wheel (curve A) and an impeller according to an aspect of the present invention (curve B);

FIG. 2 is a front view of an impeller wheel;

FIG. 3 is a rear view of an impeller wheel;

FIG. 4 is a cross-section along the longitudinal axis of an impeller wheel, including the cover; and

FIG. 5 is an impeller wheel, as shown in FIG. 2, including the cover.

DETAILED DESCRIPTION

FIG. 1 has already been described in detail above.

FIG. 2 diagrammatically shows a front view of an impeller wheel 1. A total of sixteen apertures 5 are provided in the base 3, which makes pressure equalization possible between the outer side 6 of the base 3 and the inner side of base 3 which faces the fan drive 10. According to one embodiment, fan drive 10 is electrically operated.

Apertures 5 are distributed uniformly in base 3 of impeller wheel 1. In the embodiment shown in FIG. 2, apertures 5 are configured as a slot and extend from the base center outward substantially radially. Orientation of apertures 5 corresponds with reinforcing ribs 11 which are provided on the inner side 7 of the base 3, as shown in FIG. 3, showing the side of base 3 which faces fan drive 10.

In FIG. 2, impeller wheel 1 is connected to drive shaft 8 in the center of base 3, connected by a screw 16. The longitudinal axis 18 of impeller wheel 1 coincides with drive shaft 8. Apertures 5 are spaced apart sufficiently from the connecting location. This prevents drive forces introduced at the connecting location and the base 3 from oscillating at the connecting location.

In FIG. 3, a tubular section 4 imparts a cup shape to the center part of impeller wheel 1. The cylindrical circumferential surface of tubular section 4 extends almost perpendicularly with respect to the longitudinal axis 18. Tubular section 4 encloses fan drive 10 in a similar manner to a housing. Tubular section 4 serves to accommodate eight impeller wheel blades 2 which extend outward.

FIG. 3 shows impeller wheel 1 of FIG. 2, in a rear view, i.e., of the inner side 7 of base 3. Impeller wheel blades 2 which are connected to tubular section 4 are connected to one another at their outer ends by an outer ring 17, which serves to reinforce impeller wheel 1.

To counteract a change in shape of the tubular section 4 when the impeller wheel 1 rotates, a reinforcement element 14, in the form of a reinforcing ring 15, is provided at the open end of the tubular section 4. The arrangement of this ring helps to prevent a change in shape which occurs during fan operation. The ring 15 is manufactured from a lightweight material.

Reinforcing ribs 11 are arranged on the inner side 7 of base 3. Like apertures 5, ribs 11 extend from the base substantially radially. A thickened portion of the base 3 is provided for additional reinforcement of base 3 in the region of the hole which serves to accommodate the drive shaft.

FIG. 4 diagrammatically shows a half section of an impeller wheel 1 along the longitudinal axis 18 of the impeller wheel 1, together with the cover 9, the section being positioned between two impeller wheel blades, so that the blades are not visible in FIG. 4.

Cover 9 is spaced apart from the outer side 6 of base 3. Together with tubular section 4 which serves, inter alia, as a housing, the cover 9 protects the fan drive (not shown) against corrosion and mechanical influences. In the embodiment which is shown in FIG. 4, cover 9 is fastened together with base 3 on drive shaft 8 by a screw 16.

A damping material 12 is provided between the outer side 6 of base 3 and cover 9. In one embodiment, a foam 13 serves as damping material 12. Foam 13 dampens the air flow which is produced when base 3 oscillates and ensures pressure equalization between outer side 6 and inner side 7 of base 3. In addition, the entry of spray water is prevented. However, a damping material 12 between the base 3 and the cover 9 is not necessarily required.

FIG. 5 shows a front view of impeller wheel 1 in the assembled state.

It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that one or more modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention. 

1. A fan for cooling an internal combustion engine having an impeller wheel (1) coupled to a fan drive (10) having a drive shaft (8), comprising: a base (3) for fastening the impeller wheel (1) on the drive shaft (8); a tubular section (4) adjoining said base (3); at least two impeller wheel blades (2) connected to said tubular section (4) and extend outward; and at least one aperture (5) provided in said base (3).
 2. The fan of claim 1 wherein said aperture (5) allows pressure equalization between an outer side (6) of the base (3) and an inner side (7) of said base (3) which faces the fan drive (10).
 3. The fan of claim 1 wherein said impeller wheel (1) has a cup-shaped basic shape.
 4. The fan of claim 1, wherein said base (3) has at least one reinforcing rib (11).
 5. The fan of claim 4, wherein said at least one reinforcing rib (11) is arranged on said inner side (7) of said base (3).
 6. The fan of claim 4, wherein said at least one aperture (5) is spaced apart from said at least one reinforcing rib (11).
 7. The fan of claim 1, wherein a cover (9) is provided which is spaced apart from said outer side (6) of said base (3).
 8. The fan of claim 7, wherein a damping material (12) is provided between said outer side (6) of said base (3) and said cover (9).
 9. The fan of claim 8, wherein said damping material (12) is a foam (13).
 10. The fan of claim 1 wherein at least one reinforcement element (14) is provided on said tubular section (4).
 11. The fan of claim 10, wherein said at least one reinforcement element (14) comprises a ring (15) which is arranged on an open side of said tubular section (4) which faces away from said base (3).
 12. The fan of claim 11 wherein said at least one reinforcement element (14) is manufactured substantially from a lightweight material.
 13. An impeller wheel (1) coupled to a fan drive (10), comprising: a base (3) for fastening the impeller wheel (1) on the drive shaft (8); a tubular section (4) adjoining said base (3); at least two impeller wheel blades (2) connected to said tubular section (4) and extend outward; and at least one aperture (5) provided in said base (3) wherein said impeller wheel (1) has a cup-shaped basic shape.
 14. The impeller wheel of claim 13, wherein said base (3) has at least one reinforcing rib (11).
 15. The fan of claim 14 wherein said at least one reinforcement element (14) is manufactured substantially from a lightweight material. 